bottom tap for studs- update

[jethro]

I have removed my head to change to a new gasket. This means I don't have to have extended length tap(s)
I had all ready gotten an extended bottom tap - however because of being an extended shank model- there were few choices
to pick from.
Taps have very slightly different diameters which cause the tapped hole to have a looser or tighter fit when you install the bolt or stud. The degree of oversize-ness is the "h-limit" of the tap. the numbers go something like 1 to 10- 1 making the tightest thread- and 10 loose fit. When I bought the extended bottom tap I believe it was an H-6. there were no extended ones I could find with a lower limit.

I have tried a couple of holes with this tap. I can feel a slight drag as I am going down the hole. Tapped a couple to bottom OK. Tried stud in these holes and noticed that when the stud is all the way in - or close- I can wiggle the top of the stud
just a little bit (like 1 mm) laterally. This - together with the slight drag going down tells me that this tap is a little bigger
than I would like. Seeing as how we want to maximize the holding power of the studs- I think you would want the maximum
overlapping surface area between the stud threads and the block threads- that is a close fit- as close as I can get to having a
slight drag.

It appeared that there was a much greater variety of taps in the regular shank length- so I am going to try to find more regular
metric taps - but ones with a small h-limit so I can get a snugger hole.
Maybe you think I am being picky- but I think the stud fit could be pretty important to the ultimate strength.
AND- regular taps are pretty cheap and available !

Tim

[jethro]

found some (a few) D3 limit taps at MSC.
Ordered one plug and one bottom.
just don't like having any slack in the fit.

Will see if the D3 taps will screw in without dragging (cutting)

Never found a D3 tap in an extended shank version.
That might be a reason to remove the head when installing these studs.

Talked to ARP and tried to get their opinion on the matter - but they advised that A1 had closed their stud part of their business
about 9 months ago. Sounded like he was afraid to give me an opinion.

Will report back on the updated taps- should be in tomorrow.

Tim

[jethro]

OK -
Got 2 taps from MSC- both Titanium Nitrided- both with D3 diameter limit (msammest I could find-
there seem to only be D3 and D6 available. I got one Plug type and one Bottoming type.

They do seem to make a slightly tighter clearance for both the old bolts and the new studs. They cut easily-

I have done the holes down one side on the outer edge. They all went easy. Then I tried the inboard holes nearer the cylinders. For some reason 3 of the inboard holes seem to exhibit a distinct drag on the tap. It isn't cutting anything- just
dragging. It was dragging with about half the maximum tension I would want to put on the tap. All I can figure out is that there must be a "hard chunk" of metal in the block casting (like a piece of a ring) which is so hard that it is resistant to being
cut by the tap.I have been down these holes about 5 times with the new D3 taps. Tight every time. They are snug enough I cant ass the extra lad of cutting threads too.

I tried going back to the previous d6 tap. -ran that down and then tried the smaller d3 tap again. That helped to relieve the
rotational tension somewhat- maybe half. (hope they are not many more like that)

I will have to spend quite a bit more time on these 3 holes. I noticed too that the holes were threaded to quite a bit different depths relative to the bottom of the hole. Some take only 3 or so turns- and other it looks like there could be 3/8 more hole to be threaded.....

Also I found out that A1 - who made my studs went out of the stud business about 9 months ago. So I guess no customer service questions there.

I am glad now I took the head off-

Tim

[jethro]

All most done tapping. I am using a plug tap and a bottom tap - alternating them. About 2-3 turns and then switch.
This keeps the contact area of the taps lowered which reduces the torque on the taps- which should reduce the risk of a breakage. Blow out hole with air stinger and brake cleaner.
Definitely recommend taking head off for A1 studs. (maybe not for the other brand)

Tim

[jethro]

Got all the holes tapped to bottom. 2 taps definitely easier- than 1.
Got the studs in. Put a coat of ultra-copper stray on deck and on head. New gasket (factory)
Installed and torqued A1 studs per written instructions to 115 ft-lbs.
Installed and torqued manifold.
Received new manton series 5 push rods. Installed them and the rockers tonight.
Next have to mill the valve covers.

really like the manton push rods. They beat the cummins ones azzz !
Quality is night and day better. the factory ones look like a high school kid's first day of shop class.
.095 wall chrome-molly and hard drawn /heat treated. Much better !
Got to get injectors tested next. (might as well know - right ? )

Tim